1. Technical Field
This invention relates generally to protective shields in the electrical art and, more particularly to a protective shield that is used to protect an electronic monitoring device or tire tag mounted on the inside of a pneumatic tire during a high-voltage, non-destructive test procedure. Specifically, the present invention relates to a protective device that is configured to be removably positioned over an electronic monitoring device in a pneumatic tire to protect the device from damage during a high-voltage, non-destructive test procedure.
2. Background Information
The treads of a pneumatic tire periodically wear out requiring the tire to be retreaded or replaced. Retreading tires for large trucks and vehicles is typically more economical than replacing a tire and is thus preferred in the art when the tire carcass is strong enough to be retreaded. The retreading process includes removing the worn tread package from the tire carcass and then attaching a new tread package to the carcass in a vulcanizing procedure. The retreading process results in a valuable tire as long as the carcass and new tread package are free of defects.
Tire carcasses must be tested for defects prior to retreading in order to avoid retreading a tire carcass having a defect that would immediately destroy the tire or cause the tire to fail shortly after retreading. One method of testing a tire carcass is subjecting the carcass to a high-voltage non-destructive test (hereinafter NDT) procedure. The NDT procedure includes the steps of mounting the tire carcass on a rotatable hub such that the carcass is disposed above a sensor plate. A fixed wire cage that substantially corresponds to the interior shape of the carcass is positioned inside the carcass above the sensor plate. The wire cage is energized with approximately 35,000 volts and the carcass is rotated through at least one full rotation. The rubber carcass functions to insulate the high-voltage wire cage from the sensor plate during the rotation. Any defect such as a puncture in the carcass allows the electricity to arc from the wire cage to the sensor plate. Any such arcs are sensed by the sensor plate and the defect allowing the arc is inspected to determine if it can be repaired or if the tire carcass must be scrapped. This procedure may also be performed on the carcass after it has been retreaded to check for defects.
A problem with this procedure arises when the tire carcass being tested has an electronic monitoring device (known in the art as a tire tag) mounted on the innerliner of the carcass. Two examples of such tire tags are shown in U.S. Pat. Nos. 3,787,806 and 5,500,065. A first problem is that the high-voltage test wire can snag on the tire tag and pull it from the innerliner. Another problem is that the electronic components of the tire tag are relatively sensitive and can be destroyed by the high voltage electrical environment of the NDT procedure. The components are damaged when electricity arcs between a test component and the monitoring device. The electric field created by the test components can also damage the monitoring device. A further problem is that the components of test equipment can be damaged if they snag on the tire tag. It is thus desired in the art to provide a protective device or shield that can be temporarily placed over the tire tag during the NDT procedure that shields the electronic components of the tire tag from damage and prevents the test equipment from snagging on the tire tag.